In a conventional chain tensioner, in order to fix the guide bar by providing the tension to the saw chain running along the guide bar between an engine cover and a chain cover, fixing means for attaching the chain cover to the engine cover and moving means for moving the guide lever frontward in order to provide the tension to the saw chain running along the guide bar are independent, respectively.
A structure of a chain tensioner comprising the fixing means of the guide bar and the moving means is proposed, for example, in Japanese Utility Model Publication No. 3085277. A brief explanation of this structure is provided hereinafter. As shown in FIG. 21, a driving piece 58 convexly provided with plural convex patterns 59 is attached to a guide bar 60 and a spiral orbital row 57 of a catch disk 56 having the spiral orbital row 57 is freely inserted into the convex patterns 59. The moving means of the guide bar 60 manually rotates the catch disk 56 via a driving disk 52 so as to move the guide bar in a tension direction of a saw chain 61.
On the other hand, a nut 53 screwed together with a stud bolt 63 provided in an engine cover 62 is irrotationally housed in a knob 51 disposed on a same axis as that of a driving link 52 via a polygonal seat body 54. In a fixing means of the guide bar 60, the knob 51 is manually rotated so as to fix the guide bar 60 between the engine cover 62 and a chain cover 55 while attaching the chain cover 55 to the engine cover 62.
According to the tensioner of the saw chain proposed by the Japanese Utility Model Publication No. 3085277, it is possible to move the guide bar 60 and fix it between the engine cover 62 and the chain cover 55 without using any tools.
Furthermore, according to Japanese Patent Publication No. 2729582, for example, a suspension device for a tension of the saw chain comprises, as shown in FIG. 22, a disk with the spiral groove 75 and a sliding member 73 having a protrusion (not shown) engaged with a spiral groove 83 of the disk with the spiral groove 75 on one surface, a protrusion 74 engaged with a guide bar 72 on the other surface. A moving mechanism of the guide bar is constructed by engaging a ring-like gear 82 formed in an outer circumference of the disk with the spiral groove 75 with an operation gear 78 supported by the chain cover 76.
The disk with the spiral groove 75 is rotated so that the guide bar 72 is moved in a tension direction of the saw chain 84 via the sliding member 73. On the other hand, a presser disk 79 comprises a metal nut 85 and a folded movable member 80 for pressing and fixing the metal nut 85 by a rotation so as to constitute the fixing mechanism of the guide bar. The folded movable member 80 is raised to rotate the presser disk 79 so that the metal nut 85 is screwed together with a stay bolt 71 attached to the engine cover 70. When the folded movable member 80 is folded, a locking protrusion 81 engages with a tooth row having a plurality of protrusions 77 formed on an inner circumference face of the chain cover 76 so as to restrict a rotation of the presser disk 79 via an operation gear 79.
In these tension/fixing devices for the guide bar disclosed by these publications, the fixing means and moving mechanism are constituted separately. Therefore, it is necessary to carry out the attachment of the guide bar and the chain cover by the fixing means while maintaining a state in which the guide bar is moved by the moving mechanism. Thus, as the case may be, the moving mechanism should be supported by one hand in order not to render the moving mechanism movable, and the fixing means should be rotated only by the other hand. Consequently, it is difficult to provide a tension to the saw chain with a desired tension while fixing the chain cover to the engine cover securely, and each time when providing the tension to the saw chain, an adjustment takes a lot of trouble.
In the present invention, an auto chain tensioner in which a fixing means for fixing a guide bar and a chain cover integrally comprises a moving mechanism for moving a guide bar in a back and forth moving direction is provided. Especially, an auto chain tensioner in which the moving mechanism comprises an adjustment mechanism for adjusting a moving amount of the guide bar and adjusting a tension of a saw chain.